When an electric field is applied to an object, the resulting charge separation in the object is referred to as electric polarization. Although most materials exhibit electric polarization only when an electric field is applied to the material, some materials exhibit electric polarization without an applied electric field (i.e., a spontaneous polarization). Such materials are often referred to as pyroelectric materials. For some pyroelectric materials, the direction of the spontaneous electric polarization can be switched using an applied electric field. Such materials are referred to as ferroelectric materials, and the switching of electric polarization in ferroelectric materials is analogous to the switching of magnetic moments in ferromagnetic materials. In particular, the polarization state of a ferroelectric is a non-volatile parameter that retains its value even if no power is supplied to a device including the ferroelectric.
Thus, applications of ferroelectrics to electronic device technology have been under investigation for some time. Representative examples of the state of the art include U.S. Pat. No. 6,093,242, U.S. Pat. No. 6,023,082, U.S. Pat. No. 6,080,235, and U.S. Pat. No. 6,602,720. However, it remains difficult to provide long-term stability of ferroelectric switching in connection with microelectronic devices.